Ref Number = ASPR0030
Human microbiome and climate change
Department of Child Health, Airlangga University, Surabaya Indonesia 
Human microbiome is the collection of microorganisms which live on us. They live in gut, respiratory and urinary tract, skin and saliva. They include bacteria, archaea, fungi and protozoa. Some of the organism are useful for human, most have no known effect, they just live with us as symbions. The most known are the gut flora, which might be useful for health. 
Climate change as global warming are observed has deleterious effect on human health, in more severe form of clinical appearance and in increased recurency of infectious diseases. Some questions are raised on the impact of warmer environment on the gut microbiome and overall human health.  
The change of environmental temperature which alters the digestive performance and gut microbiota were studied in terrestrial amphibian, the red-backed salamander. It is assumed that the nature - of the digestive performance of ectotherm animal dependent temperature - is related to physiological changes and adaptation to the local climate conditions. Ectotherm is used in this study, as their digestive performance is temperature dependent, can be measured by foraging rate, digestive efficiency, energy assimilation, gut passage time and metabolic responds to feeding. Thermal sensitivity is measured by taking comparison with the standard performance curve which also demonstrated in other ectothermic taxa. Study demonstrated that microbial communities living in their gut have mayor impact on digestive performance. Gut microbiota may enhance digestion through fermentation of various plant, detoxification of unpalatable food or provision of alternative energy in food scarcity. The relationship of microbiome and energy production in mammal is very important in ectothermic vertebrates, as their gut are house for diverse microbial communities with high level of fermented activity. The gut microbiota is supposed to provide digestive services with a dependency on their surrounding temperature. The hypothesis is that digestive performance, energy intake, energy assimilation, diversity and community composition of gut microbiota, digestive efficacy, the abundanc bacterial taxa, is significantly impacted by environmental temperature and correlate with the host digestive performance. 
The study measured the digestive performance and gut microbiota diversity of salamander in 3 groups of external temperature, 100C, 150C, 200 C.  Red-backed salamander were collected, acclimated for 4 weeks, fed with the same drosophila. They are fed, skin and feces were collected, until the digestive tract was clear, acclimated again for 7-10 day for next trial in different temperature. Energy assimilation and efficiency were calculated for each trial. Fecal sample for microbiome were collected from each feeding trial ended, sample were kept in -800 until processing.  
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The gut microbial diversity was decreased by higher temperature, certain genera which were abundant maximally in the temperature 150 were relatively low at the 100 and 200. The finding demonstrated that the environmental temperature significantly impact digestive performance which is consistent with the understanding that temperature has impact on ectotherm physiology. Increasing temperature will reduce the relative abundancy from 25 to 14, genus Janthinobacterium which 5.8% at 100 C diminished to 0.14% at 200 C. This genus occur in the skin and shown to protect individuals from a globally devastating fungal disease chytridiomycosis. Increase temperature will make salamander more sensitive to cutaneous pathogens. Citrobacter which caused bacterial dermatosepticaemia shown a no linier relationship with temperature, denotes that shifting of temperature will depress the immune respons of the amphibian, with a mechanism yet to be tested further. Some other Sphingolipid, Roseococcus, Cellvibrio, Strephomonas, especially Cellvibrio especially promote host energy assimilation, temperature induced changes will provoke an alter digestive performance, along with the change of microbiota diversity. This study reveal that the temperature alters microbiome which in turn reduced the animal performance. Mechanism might vary di every animal. 
Other studies also revealed the possible mechanism by which an additional gut microbiome will alter gut and also systemic immunity. Lactobacillus rhamnosus gg and L plantarum showed the ability to inhibit the attachment of the enteropathogenic Escherichia coli in intestinal tract. Probiotics modulated the intestinal microbiota by maintaining the balance and suppressing the growth of pathogens bacteria in the gut and stimulate the mucosal immune system to begin a network of signal through Toll Like Receptor to induce cytokines and chemokines. Macrophage and dendritic cells play an important role since they to activate lamina propria without inducing an inflammatory pattern. Macrophage chemoattractant 1 send signals to activate mucosal immune system characterize by increasing production of IgA, in the gut, brochus and mammary glands.  Probiotics reinforce intestinal barrier by an increase of musin, tight junction protein, GOBLET and PANETH cells and also increase the microbial activity of the spleen and peritoneal macrophage to protect against different pathogens. In case of malnutrition or obesity, probiotic is able to recover both the intestine and thymus damaged.  Will global warming impact the benefit effect of microbiome on human?  There is no definite answer yet, but the study on terrestrial amphibian had open a view on which adaptive mechanism to a higher temperature will effected the function or diversity of the gut microbiota. 
Keywords: Global Warming; Human Microbiome; Salamander ; Efficient Metabolism
Galdeano CM, Cazorla SI, Dumit JML, Velez E, Perdigon G. Beneficial effects of probiotic consumption on the immune system . Ann Nutr Metab 2019; 74:115-124
Fontaine S S, Novarro AJ, Kohl KD. Environtmental temperature alters the digestive performance andgut microbiota of a terrestrial amphibian. Journal of experimental biology (2018) 221,jeb 187559.doi.10.1242/jeb.187559 
Blacher E, Levy M, Tatirovsky, Elinav E. Microbiome modulated metabolites at the interface of host immunity. The Journal of Immunology 2017;198 :572 
Disclaimer: The Views and opinions expressed in the articles are of the authors and not of the journal.
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